Molybdenum　disulfide　(MoS2),　a　promising　non-precious　electrocatalyst　for　the　hydrogen　evolution　reaction　with　two-dimensional　layered　structure,　has　received　increasing　attention　in　recent　years.　Its　electrocatalytic　performance　has　been　limited　by　the　low　active　site　content　and　poor　conductivity.　Herein,　we　report　a　facile　and　general　ultrafast　laser　ablation　method　to　synthesize　MoS2　quantum　dots　(MS-QDs)　for　electrocatalytic　HER　with　fully　exposed　active　sites　and　highly　enhanced　conductivity.　The　MS-QDs　were　prepared　by　ultrafast　laser　ablation　of　the　corresponding　bulk　material　in　aqueous　solution,　during　which　they　were　partially　oxidized　and　formed　defective　structures.　The　as-prepared　MS-QDs　demonstrated　high　activity　and　stability　in　the　electrocatalytic　HER,　owing　to　their　very　large　surface　area,　defective　structure,　abundance　of　active　sites,　and　high　conductivity.　The　present　MS-QDs　can　also　find　application　in　optics,　sensing,　energy　storage,　and　conversion　technologies.